Modern methods for production of iron and steel from iron ore still have a recognizable link to early historical methods despite ongoing research to improve the process. Conventional techniques still involve heating of iron ore in a furnace in the presence of a solid carbon-containing material such as coke. Due to the nature of the process, including the substantial heat requirements for forming molten iron (and other metals), conventional processes for reducing iron oxides to form iron also result in generation of substantial quantities of carbon dioxide. This is due in part to use in typical processes of coal or other highly polluting fuels to provide the necessary heat.
Molten carbonate fuel cells utilize hydrogen and/or other fuels to generate electricity. Options for generating hydrogen for use in a molten carbonate fuel cell include reforming methane or other reformable fuels within the anode of the fuel cell, or reforming fuel in an associated reforming zone that is either internal to or external to the fuel cell. Reformable fuels can encompass hydrocarbonaceous materials that can be reacted with steam and/or oxygen at elevated temperature and/or pressure to produce a gaseous product that comprises hydrogen.
Traditionally, molten carbonate fuel cells are operated to maximize electricity production per unit of fuel input, which may be referred to as the fuel cell's electrical efficiency. This maximization can be based on the fuel cell alone or in conjunction with another power generation system. In order to achieve increased electrical production and to manage the heat generation, fuel utilization within a fuel cell is typically maintained at 70% to 75%.
U.S. Published Patent Application 2011/0111315 describes a system and process for operating fuel cell systems with substantial hydrogen content in the anode inlet stream. The technology in the '315 publication is concerned with providing enough fuel in the anode inlet so that sufficient fuel remains for the oxidation reaction as the fuel approaches the anode exit. To ensure adequate fuel, the '315 publication provides fuel with a high concentration of H2. The H2 not utilized in the oxidation reaction is recycled to the anode for use in the next pass. On a single pass basis, the H2 utilization may range from 10% to 30%. The '315 reference does not describe significant reforming within the anode, instead relying primarily on external reforming.
U.S. Published Patent Application 2005/0123810 describes a system and method for co-production of hydrogen and electrical energy. The co-production system comprises a fuel cell and a separation unit, which is configured to receive the anode exhaust stream and separate hydrogen. A portion of the anode exhaust is also recycled to the anode inlet. The operating ranges given in the '810 publication appear to be based on a solid oxide fuel cell. Molten carbonate fuel cells are described as an alternative.
U.S. Published Patent Application 2003/0008183 describes a system and method for co-production of hydrogen and electrical power. A fuel cell is mentioned as a general type of chemical converter for converting a hydrocarbon-type fuel to hydrogen. The fuel cell system also includes an external reformer and a high temperature fuel cell. An embodiment of the fuel cell system is described that has an electrical efficiency of about 45% and a chemical production rate of about 25% resulting in a system coproduction efficiency of about 70%. The '183 publication does not appear to describe the electrical efficiency of the fuel cell in isolation from the system.
U.S. Pat. No. 5,084,362 describes a system for integrating a fuel cell with a gasification system so that coal gas can be used as a fuel source for the anode of the fuel cell. Hydrogen generated by the fuel cell is used as an input for a gasifier that is used to generate methane from a coal gas (or other coal) input. The methane from the gasifier is then used as at least part of the input fuel to the fuel cell. Thus, at least a portion of the hydrogen generated by the fuel cell is indirectly recycled to the fuel cell anode inlet in the form of the methane generated by the gasifier.
An article in the Journal of Fuel Cell Science and Technology (G. Manzolini et. al., J. Fuel Cell Sci. and Tech., Vol. 9, February 2012) describes a power generation system that combines a combustion power generator with molten carbonate fuel cells. Various arrangements of fuel cells and operating parameters are described. The combustion output from the combustion generator is used in part as the input for the cathode of the fuel cell. One goal of the simulations in the Manzolini article is to use the MCFC to separate CO2 from the power generator's exhaust. The simulation described in the Manzolini article establishes a maximum outlet temperature of 660° C. and notes that the inlet temperature must be sufficiently cooler to account for the temperature increase across the fuel cell. The electrical efficiency (i.e. electricity generated/fuel input) for the MCFC fuel cell in a base model case is 50%. The electrical efficiency in a test model case, which is optimized for CO2 sequestration, is also 50%.
An article by Desideri et al. (Intl. J. of Hydrogen Energy, Vol. 37, 2012) describes a method for modeling the performance of a power generation system using a fuel cell for CO2 separation. Recirculation of anode exhaust to the anode inlet and the cathode exhaust to the cathode inlet are used to improve the performance of the fuel cell. The model parameters describe an MCFC electrical efficiency of 50.3%.
U.S. Patent Application Publication 2013/0081516 describes a method for direct production of iron slabs and nuggets from ore without pelletizing or briquetting. The method involves forming a mixture of fine particles of iron ore with fine particles of a carbon source such as biomass, coke, or coal. The mixture of fine particles is passed through a linear furnace to form metallic iron. An excess of biomass, coke, or coal can be used to allow excess production of CO and H2 that can be recovered as syngas from a gas phase environment in the furnace.
U.S. Pat. No. 6,524,356 describes a method for performing direct iron reduction in a shaft furnace using reformed methane as a source of synthesis gas. The method further describes introducing additional natural gas into the shaft furnace as a source of carbon for incorporation into the iron.